SEATTLE — William E. Boeing Jr., a son of aerospace pioneer William Boeing Sr. who championed and remained fascinated by flight throughout his life, has died at age 92.

He died Wednesday night at his home in Seattle, said Mike Bush, a spokesman for The Museum of Flight, which Boeing Jr. helped create. The cause was not immediately known.

Boeing Jr. did not work at his father’s company. He pursued a career in commercial real estate. But he nevertheless witnessed how the airplane maker helped transform Seattle from a backwater frontier town to an aerospace hub in the early part of the 20th century, and he became a champion of the industry and aerospace education.

“Bill’s impact on the social and economic development of the Puget Sound has greatly benefited generations in the community,” Boeing Chairman Jim McNerney said Thursday in a written statement. “As a leading light in the creation and expansion of The Museum of Flight, he helped showcase our heritage and inspire generations to join in and further advance the science and business of aerospace.”

In 1975, Boeing Jr. paid to move and restore Boeing’s first factory — a building on Seattle’s Duwamish River known as the “Red Barn,” where his father began building floatplanes in 1916 and where he had fond boyhood memories. It was shipped 2 miles by barge to its current location at King County International Airport, where it became part of the museum.

“Mr. Boeing was an insightful and driving force of The Museum of Flight from its earliest days,” the museum said in a statement posted on its website. “True to his family name, aviation always held a special place in his life, and as a trustee at the museum, he led the way in turning the institution from a small, local attraction to one of international importance.”

Boeing Jr. had served as a trustee at the museum, where he was beloved by the staff, Bush said. Last year, The Boeing Co. donated the third 787 airliner ever manufactured to the museum, and the museum honored the company in June with its Red Barn Heritage Award. Boeing served as chairman of the event and gave its keynote speech, telling funny and poignant stories of his father and the early days of aviation, Bush said.

Boeing Jr. would sometimes recall how he liked going to Boeing’s factory as a boy not so much for the planes, but for the balsa wood used in their construction.

“I thought that was the greatest find of anything,” Boeing Jr. said in a 2012 biographical film produced by Storyteller Communications. “I thought it was more important than an aircraft or flying or anything else because the wood was strong and light. I could make my battleship model out of it.”